Risk factors for HIV vary between African cities, need tailored responses

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A comparative study in three large cities in southern Africa has found big differences in risk factors for acquisition of HIV infection, emphasising the importance of locally tailored HIV prevention strategies and up-to-date information on local risk factors.

The study looked at behavioural risk factors associated with acquiring HIV infection in 5000 sexually active women in Harare, Durban and Johannesburg who took part in a large trial of an HIV prevention method based on use of the diaphgram.

Sue Napierala Mavedsnege and colleagues report the findings of their prospective cohort analysis in the advance online edition of the Journal of Acquired Immune Deficiency Syndromes. 

Glossary

person years

In a study “100 person years of follow-up” could mean that information was collected on 100 people for one year, or on 50 people for two years each, or on ten people over ten years. In practice, each person’s duration of follow-up is likely to be different.

adjusted odds ratio (AOR)

Comparing one group with another, expresses differences in the odds of something happening. An odds ratio above 1 means something is more likely to happen in the group of interest; an odds ratio below 1 means it is less likely to happen. Similar to ‘relative risk’. 

prospective study

A type of longitudinal study in which people join the study and information is then collected on them for several weeks, months or years. 

longitudinal study

A study in which information is collected on people over several weeks, months or years. People may be followed forward in time (a prospective study), or information may be collected on past events (a retrospective study).

clinical trial

A research study involving participants, usually to find out how well a new drug or treatment works in people and how safe it is.

A total of 309 incident HIV infections were identified. Durban reported the highest incidence rate, followed by Johannesburg and then Harare (6.75 per 100 person years, 95% CI: 5.74-7.93; 3.33 per 100 person years, 95% CI: 2.51-4.44; 2.72 per 100 person years CI: 2.26-3.26, respectively).

Having more than one partner in the last three months was the only common factor associated with HIV incidence.

The majority of the estimated 35 million people living with HIV live in sub-Saharan Africa where 70% of all new infections occur. Women represent over 60% of all infections. Southern Africa, with the highest regional prevalence, reflects different phases of the epidemic.

In Zimbabwe, with an estimated prevalence of 14.3%, the epidemic began early, peaked in 1998 with a subsequent decline in incidence and prevalence.

From 1990-1998 South Africa had an exponential increase followed by a moderate increase until 2004 when apparent stabilisation began. In 2008 estimated provincial prevalence rates ranged from 5.3% to 25.8%.

In Gauteng province, with Johannesburg its largest city, prevalence appears to have peaked in 2002 at 20.3% and declined to 15.2% in 2008. In contrast, Kwa Zulu Natal province where Durban is the largest city, estimated prevalence rose from 15.7% in 2002 to 25.8% in 2008.

While cross-sectional studies looking at risk factors associated with HIV have taken place in Zimbabwe and South Africa, few have looked at risk factors for HIV incidence in women.  A better understanding of these factors within local contexts will help develop targeted interventions so reducing transmission.

The authors looked at factors associated with differences of HIV incidence among women in Harare, Johannesburg and Durban enrolled between September 2003 and September 2005 in the Methods for Improvement of Reproductive Health (MIRA) study, a randomised clinical trial to look at the effect of the diaphragm plus lubricant gel for the prevention of HIV. The intervention did not reduce HIV incidence.

The authors undertook a prospective cohort analysis of trial participants who were followed for a median of 21 months (12-24 months).

Socio-demographic, biological and behavioural data were collected at baseline and at quarterly visits. Testing for HIV and STIs were conducted at each quarterly visit.

Each location had distinct characteristics as well as different patterns of individual risk factors.

In Harare women were more likely to live with their partner, be employed and not use alcohol or drugs but more likely to wipe inside their vagina. While they had a later sexual debut and fewer partners than in Durban or Johannesburg there was more transactional sex (for money, food, drugs or shelter) within the last three months.

Early sexual debut was more common in Durban, while in Johannesburg consumption of alcohol within the last three months, multiple sexual partners and sex under the influence of drugs or alcohol were more likely.

Sexually transmitted infections (STIs) were important risk factors in Harare and Durban (prevalent herpes simplex virus AHR=2.56, 95% C: 1.61-4.06; incident herpes simplex virus AHR= 12.6, 95% CI: 2.13-21.87; gonorrhoea AHR=6.82, 95% CI: 2.13-21.87 and prevalent herpes simplex AHR=1.64, 95% CI: 1.07-2.52; gonorrhoea AHR=4.40, 95% I: 2.07-9.39, respectively.

Multiple partners and sex with a partner under the influence of alcohol or drugs significant increased the risk in Durban (AOR=1.78, 95% CI: 1.11-2.85 and AOR= 1.51, 95% CI: 1.05-2.16, respectively, whereas in Johannesburg early sexual debut was a strong predictors of getting HIV(AOR= 2.60, 95% CI: 1.30-5.17).

In Harare and Johannesburg 20.2 % and 22.3% of HIV infections, respectively, were attributable to wiping inside the vagina. Wiping inside the vagina has been independently associated with decreased condom use

In Harare over 96% of women were living with their partner; the median number of lifetime partners was 1.3. This implies, note the authors, most HIV infection was acquired from their live-in partner, yet 25% did not know their partner’s status.

The authors note the strengths of the study include its longitudinal study design and large sample size.

A limitation is that the study was conducted among clinical trial participants with strict eligibility criteria.

The authors suggest “as an epidemic matures more transmission occurs within stable partnerships, and we may see this...in South Africa. As the epidemic wanes, as… in Zimbabwe, we may begin to see…HIV transmission among young people and high risk core groups become increasingly important drivers of the epidemic.”

The significant differences in drivers of HIV incidence in the three locations support targeted HIV programming based on the local situation and epidemiology as the most effective approach to reduce HIV incidence among women, the authors conclude.

References

Napierala Mavedzenge S et al. Determinants of differential HIV incidence among women in three southern African locations. JAIDS advance online edition, doi: 10.1097/QAI.0b013e3182254038, 2011.